Jockey Carlos H. Marquez Jr. injured his right leg in the starting gate at Monmouth Park.

Angelo Chinnici, the track’s medical director, said Marquez had “a pretty serious bruise on his right calf” and was sent to a hospital for precautionary X-rays.

Track officials did not immediately disclose how the 43-year-old Marquez was injured yesterday. The incident occurred just before the fifth race.

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Rush Now drew off in the stretch to win the $75,000 Spend a Buck Stakes at Monmouth Park, beating Uncle Otto by 4 1/4 lengths.

Trained by Anthony Dutrow and ridden by Joe Bravo, the 3-year-old colt led most of the way and covered the mile and 70 yards over a fast track in 1:40 3/5 and returned $4, $3 and $2.20. It was the fourth win in nine career starts for Rush Now, who has now earned $158,765.

Uncle Otto paid $11.80 and $3.80, while Malibu Glow was another 3 1/4 lengths back in third and returned $2.20.